Polyester resins are used for various applications such as films, fibers, mechanical components, and electronic components due to excellent properties thereof in terms of heat resistance, mechanical strength, transparency, chemical resistance, and the like. For example, polyester resins can be used as materials for reflectors, scramblers, and/or housings of light emitting diodes (LEDs), which have received recent attention as a replacement for many existing light sources.
A reflector for light emitting diodes is a component for improving luminous efficacy of a light emitting diode chip by reflecting light emitted from the light emitting diode chip toward a front side thereof while enveloping and protecting the light emitting diode chip. The reflector can suffer from significant deterioration in reflectance and extraction capability due to discoloration after extended use.
Inorganic particles can be added to the reflector in order to improve reflectance of the reflector by taking reflectance and whiteness into account. However, since the reflector can suffer from change in color upon molding and significant reduction in reflectance over time, it can be difficult to obtain sufficient brightness.
There has also been an attempt to manufacture a reflector using a ceramic material. There is a drawback, however, in that the ceramic material is uneconomical due to deterioration in productivity despite excellent heat resistance and chemical resistance thereof.
Therefore, for extension of lifespan of light emitting diode illumination devices, there is a need for a polyester resin composition which exhibits minimal or no change in reflectance and whiteness even after extended use, thereby securing excellent reflectivity and yellow index.